Another confusing thing is doing this:

    xxxxx-xxxxx-xxxxx-xxxxx

Instead of something like this:

    xxxxx-xx-xxxxx-xxx-xxxxx

Something could also be said about such scheme lacking the embedding of a checksum.

Here's an IBAN (bank account number) in the EU (which thankfully are using a checksum as part of the account number):

    LU29 0022 1712 5582 7000
      ^^
      ||
      two checkdigits

Also some companies think they're "smart" because they pick numbers like this:

    LU29 002 0000 0001 8000

Repeating the same digit, usually a zero, a shitload of time ain't smart. It's fucking dumb.